An answer from a colleague TurboTax Hal_Al:
It won't be anywhere on the 1099-Q. If it's not in the plan name (e.g."Ohio College Advantage"), you'll have to ask the plan administrator. It's usually your home state, but that's not always the case. The plan's address is not a reliable indicator, as they use financial institutions all over the country. The Ohio plan has a Kansas City address.
